Class 8 General Science Notes: - Unit-5: The Periodic Table of Elements: Solved Exercise (Long Questions and Answers)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

C. Long Questions

Q1. How can you locate an element in the periodic table: Identify the location of the following element in the periodic table?

a) Aluminum (Atomic No.13)
b) Silicon (Atomic No.14)
c) Fluorine (Atomic No.9)

Ans:

a) Location of Aluminum in the periodic table:

1. Atomic No. = 13
2. Electronic configuration of Aluminum 2 (K), 8 (L), 3 (M)
3. Valence electrons are 3. So the group of Al is III A
4. Valence shell Al is M shell so, the period of Al is 3.

b) Location of Silicon in the periodic table:
1. Atomic No. = 14
2. Electronic configuration of Aluminum 2 (K), 8 (L), 5 (M)
3. Valence electrons are 4. So the group of Al is IV A
4. Valence shell Al is M shell so, the period of Al is 3.

c) Location of Fluorine in the periodic table:
1. Atomic No. = 9
2. Electronic configuration of Aluminum 2 (K), 7 (L)
3. Valence electrons are 7. So the group of Al is VII A
4. Valence shell Al is K shell so, the period of Al is 2.

Q2. Justify that the properties of metals make them suitable for making many objects or their parts. Explain with three examples.

Ans:

1. Uses of metals in making jewelry:

Gold and Silver are soft and shiny, easy to bend and mold. It can be easily shaped into rings, bangles, and necklaces. Their shiny appearance makes jewelry very ductile.

2. Uses of metals in making bicycles and aeroplane:

Aluminum is a malleable, light, and strong metal. It is used to make bicycle frames and rims. It Possesses high strength used to make aeroplanes, Solar panels, and other aeroplanes technology.

3. Uses of metals in making bridges and buildings:
Iron is used in the construction of bridges and buildings because; it can resist high lead stress and strain.

Unit-5: The Periodic Table of Elements: Solved Short Questions and Answers

Class 8 General Science Notes

Source: General Science Book (National Book Foundation, Pakistan)

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